A 31-year-old mother has been arrested for allegedly dumping her newborn baby on the side of the road, shortly before a rubbish truck was due to do its rounds, private security company Reaction Unit South Africa (Rusa) said on Tuesday.

Rusa spokesperson Prem Balram said members of the KwaZulu-Natal community alerted them after a local scrap collector heard the baby crying. Balram said the baby was found around 2.29pm on Monday.

The baby boy was wrapped in a garbage bag and denim material.

"They [paramedics] cut the umbilical cord which was still attached to the placenta. The child was examined and found to be free of injury," Balram said.

He said, had the child not been found in time, a municipal bin truck would have picked the child up with the rest of the rubbish.

The baby was transported to hospital. The newborn weighed about 2kg.

After receiving information from the community, Rusa said they traced a woman suspected of being the mother, who lived about 100m away from where the baby was dumped.

Balram said the woman initially denied it but then told their officers that she had concealed her pregnancy for nine months due to her children being from two different fathers.

Her parents said they did not know about the pregnancy.

"After going into labour [on Monday morning] she managed to naturally deliver the baby in her bathroom while her 11-year-old son and nine-year-old daughter were at school and her parents were at work," Rusa said.

KwaZulu-Natal police spokesperson Thulani Zwane said the woman was charged with child abandonment.

She is expected to appear in court soon.